The field of this invention is that of condition responsive switches and the invention relates more particularly to switches using dished disc elements which move between original and inverted dished configurations with snap action in response to the occurrence of selected temperature or pressure conditions.
The conventional condition responsive switches have a contact arm movable between first and second switch positions, have a spring biasing the arm to one switch position, and have a dished disc element movable between original and inverted dished configurations with snap action for moving the switch between switch positions in response to the occurrence of selected temperature or pressure conditions. Such switches are intended to perform selected control functions in response to the occurrence of the selected temperatures or pressures in a zone to be monitored but it is found that forces applied to the disc elements during assembly in the switches alter the temperatures or pressures at which the disc elements move for actuating the switches. Various switch structures have been proposed for limiting such variations in forces applied to the discs during switch manufacture, assembly, and use so that the switches will display consistently and reliably reproducible condition response characteristics. However, it is found that reaction forces applied to the discs due to overtravel of the discs during snap acting disc movement for closing switch contacts in known switch structures frequently result in undesirably large variations in the thermal or pressure response characteristics of the switches.